We have encountered this before and started bringing along the Frigidaire 50 pint/day dehumidifier we normally use in the garage. This is when we are at the coast or cold weather camping w/ electrical hookup. Keeping the humidity at 60% or below keeps the windows clear. We'll get it down to 50% and then shut it off overnight. Windows and vents are kept closed. In the morning humidity will be back up to 70% and we just turn it on again. This unit consumes 470 watts.
For road trips where we don't take the big unit we will take the small Eva-Dry EDV-2200 unit which has much less but some capability and will leave it running all the time if plugged in and humidity is high. It uses Peltola technology and consumes about 80 watts.